Cooling Device

ABSTRACT

A cooling device is based on the cooling effect exhibited by high-voltage, 4 4.5 kV, unidirectional pulses discharging across a spark gap ( 2 - 13 ) in less than 100 ns. The cooling effect is extended spatially by an emitter ( 2 - 12 ) comprising two ( 3 - 2,3 - 4 ) coaxial metallic tubes that are electrically isolated from the spark gap electrodes. Such a device is particularly suitable for air conditioning in both residential and transport applications.

This invention relates to the field of temperature regulation and, inparticular, to a device for cooling enclosed or confined spaces.

Cooling devices for maintaining a room, car or other enclosed space at acomfortable temperature are well known. The majority are based on forcedair systems that may incorporate some form of cooling of the air.Cooling is generally based on the thermodynamics of condensation andevaporation of a refrigerant gas. On condensation of a gas to a liquid,heat is rejected to the environment and on evaporation of a liquid, heatis absorbed. The evaporation/condensation cycle is driven bycompression. In conventional air conditioning units the compression isdriven by mechanical work that is normally provided by an electricalmotor. Alternatively, sorption devices are driven by the adsorption orabsorption of the refrigerant gas (or sorbate), such as ammonia, by asolid or solid/liquid sorbent.

A major problem with these prior art air-conditioning systems is thatthey are relatively power-hungry to operate. Effective operation usuallyrequires a large amount of electricity, which itself is likely to havebeen generated at some cost to the environment. Although devices basedon a sorption cycle offer some improvement, this technology is by nomeans mature and very few practical devices have been developed. Withthe substantial growth in demand for air conditioning units in warmdeveloping countries such as China and India, the burden placed on theelectricity supply is becoming critical. There is accordingly anincreasing need to improve the energy efficiency of air-conditioningdevices. In particular, a more energy-efficient system offers thepossibility that it may be operated independently of the infrastructureof an electricity grid. This makes it suitable not only for use in moreremote areas but also in a moving environment such as the carriages ofan underground railway.

A further problem presented by prior art cooling devices is thepotentially hazardous nature of the refrigerant gas used. Ammonia,alcohols, hydrogen, hydrocarbons, hydrofluorocarbons and carbon dioxidehave all been used in cooling systems. The potential risks fromemploying such substances are of course more significant if using in aconfined space, such as an underground room or carriage. Most prior artcooling devices also suffer from high CO₂ emissions, which further harmthe environment.

There is accordingly a growing need to provide an alternative form ofcooling device, which is more environmentally-friendly than those knownin the prior art.

The present invention provides a cooling device comprising a highvoltage source connected to a spark gap and controlled by a timingmeans, wherein the source and timing means are arranged to generateunidirectional high voltage pulses which are discharged in short andregular impulses across the spark gap and the device also includes anemitter located in the vicinity of an electrode of the spark gap andelectrically isolated therefrom.

A device according to the present invention creates a source of highvoltage direct current pulses which are discharged in very shortimpulses, preferably less than 100 ns duration, through a spark gap. Asa result of this process, heat is withdrawn from the atmospheresurrounding the spark gap. The cooling effect is highly localised aroundthe discharge spark and so the emitter is used to provide a means ofdelocalisation. That is, the emitter distributes the cooling effect overa larger volume.

A cooling device that operates according to this principle is radicallydifferent from those known in the prior art. Whereas prior art devicesare based on a refrigerant condensation/evaporation cycle, the presentdevice is based on a cooling effect produced by a high voltageelectrical discharge.

It is known that a high voltage electrical discharge can induce cooling.In nature, atmospheric cooling in the region of a lightning strike hasbeen observed. Temperature drops have also been measured in a large coilof wire connected to a cold cathode arc switch. It is believed that sucheffects result from organising (or cohering) fluctuation energy such asthermal or quantum zero point fluctuation energy (the Zero Point EnergyField). The pulsed disruption of a high voltage supply will perturb theZPEF of a system, which results in heat being absorbed from itssurroundings. That is, a cooling effect is stimulated from the ZPEF. Adevice harnessing this effect may be used to cool the space in which itis located.

A cooling device based on this principle advantageously achieves coolingwithout the use of potentially hazardous refrigerant. Moreover, thepower required to generate a suitable electrical discharge is far lessthan that required to operate conventional cooling devices. A device canreadily be constructed that consumes less than 1% of the energy used bycurrent air cooling technology to achieve the same effect.

Such a device has numerous applications, primarily in the field of airconditioning. In addition to its environmental credentials, the deviceof the present invention may be far smaller than currently available airconditioning units. This renders it even more attractive to applicationson mobile or non-permanent locations such as trains, cars, boats andcaravans.

In order to provide the cooling effect, it is preferred that the highvoltage source is arranged to provide a voltage of at least 3 kV and,more preferably, at least 4 kV.

The high voltage source may comprise a medium voltage source, timingcontrol means for timing power output from said source in medium voltagepulses, a transformer arranged to convert the medium voltage pulses tohigh voltage pulses and a rectifier arranged to convert the high voltagepulses to a unidirectional signal. Such an arrangement means that themajority of pulse-shaping and manipulation is carried out in the mediumvoltage regime. Components that are capable of controlling high voltageare far more expensive to produce and suffer from problems withreliability. By operating primarily in the medium voltage regimetherefore cheaper, more reliable, electronic components are readilyavailable, which makes the cooling device more reliable to operate andmore economic to build.

The medium voltage source itself may comprise a storage device forstoring charge at medium voltage and which is discharged by operation ofthe timing control means. The storage device may be a capacitor or abank of capacitors. A suitable capacitance may be in the region of 50μF, and preferably around 47 μF. It may alternatively be an inductor.

The capacitor is preferably charged by a circuit comprising a lowvoltage source, a pulse generator arranged to produce an alternatingsignal from the low voltage source, a second transformer arranged toconvert low voltage input to a medium voltage output and a rectifierarranged to rectify alternating signal input to direct current output.

The spark gap preferably comprises first and second electrodes sealedwithin a chamber and separated by an insulating gap. The sealing chamberprevents the electrodes from becoming contaminated, which may inhibitgeneration of a discharge spark.

The electrodes are preferably dome shaped, which discourageslocalisation of spark emissions at a particular point on their surfaceand hence may prolong their useable life.

It is further preferred that the electrodes are made of chrome- ornickel-coated steel. The chamber may be filled with argon or othersuitably inert gas.

The emitter may comprise inner and outer thin-walled coaxial tubes,which are coaxially mounted about an electrode connection lead. Thetubes should be good electrical conductors and are therefore preferablymetallic or made from ceramic materials with high conductivity. Metalsare generally cheaper and therefore preferred.

The tubes preferably have internal diameters in the range 6 mm to 14 mmand lengths in the range 7 mm to 20 mm.

In a second aspect, the present invention provides a method ofgenerating a cooling effect, the method comprising the steps of:—

-   (a) Repeatedly applying a high-voltage, unidirectional pulse of    electricity between a pair of electrodes in a gaseous environment,    thereby causing sparking between the electrodes; and-   (b) Diffusing a cooling effect resulting from the sparking by means    of an emitter located in the vicinity of the electrodes.

The pulse is preferably of voltage higher than 4 kV and of durationshorter than 100 ns.

By way of example only, a cooling device made according to the presentinvention will now be described in detail, reference being made to theaccompanying drawings, in which:

FIG. 1 is an overview of the process by which a spark that is capable ofeffecting an environmental cooling is generated.

FIG. 2 is a schematic of a circuit design, suitable for generating acooling discharge.

FIG. 3 is a detailed drawing of a spark gap and emitter.

FIG. 4 is a detailed circuit design for generating a spark that issuitable for effecting cooling.

Referring initially to FIGS. 1 and 2, the steps carried out by andcomponents of an electrical circuit for a cooling device in accordancewith the present invention are shown. At a first step 1, aunidirectional medium direct current voltage, of around 225V, is createdand stored in a control capacitor 2-6 (FIG. 2). Alternatively, a bank ofcapacitors may be used.

At step 2, the capacitor 2-6 is discharged into the primary coil of afirst step up transformer 2-9 (FIG. 2) under control of a timer circuit2-8 to create alternating pulses at around 4500 V.

At step 3, the 4.5 kV output from the first step up transformer 2-9 isrectified to create high voltage unidirectional pulses.

At step 4, the pulses are discharged in very short impulses, of lessthan 100 ns duration, through a spark gap 2-13 located in the vicinityof an emitter 2-12. The emitter 2-12 spreads or extends a cooling effectthat is stimulated by the impulsed discharge. This therefore withdrawsheat from the emitter/spark gap environment, which lowers thesurrounding temperature. In a typical application, a device containingthe emitter 2-12 and spark gap 2-13 would be placed in a room and theeffect used to cool the air within the room.

The electronic components used to generate unidirectional high voltageimpulses, which give rise to the cooling effect, will now be describedin more detail with reference to FIG. 2. FIG. 2 illustrates a schematicof a circuit design, suitable for generating a spark in conjunction withan emitter that may be used to produce a cooling device in accordancewith this invention. It is the discharging of the control capacitor 2-6that is central to the generation of a suitable discharge spark.

A low voltage direct current power supply, 2-1, such as a regulatedmains adaptor or battery, powers a square wave generator 2-2 whoseoutput is in turn connected to a second step up transformer 2-3. Abridge rectifier 2-4 takes its input from the transformer 2-3 output,and has a diode 2-5 and the control capacitor 2-6 connected in parallelacross its output.

These components are used to charge the capacitor 2-6 as follows. Thelow voltage direct current supply 2-1 typically provides around 500 mAat 9V. The square wave generator 2-2 converts this signal to a squarewave, which is applied across the second step up transformer 2-3. Thistransformer 2-3 is arranged to convert 9V input to a medium voltageoutput of around 225V. The output signal from the transformer 2-3 istherefore an alternating signal, at around 225V. The bridge rectifier2-4 converts this signal to a direct current, maintaining the mediumvoltage level, reversals of current being prevented by the diode 2-5.The medium voltage unidirectional direct current is stored in thecapacitor (or bank of capacitors) 2-6. Typically, the capacitanceprovided by this capacitor or bank is around 47 μF.

Once the energy is stored in capacitor 2-6, the discharging of thiscapacitor at the medium voltage level is the next step 2 (FIG. 1) in theprocess. A timing control circuit 2-8 and the input to the firsttransformer 2-9 are connected in series across the output of thecapacitor 2-6. The timing circuit 2-8 thereby regulates the capacitordischarge into the primary coil of the transformer 2-9. If the timingcircuit 2-8 is on, current is discharged from the capacitor 2-6 andinput to the first step up transformer 2-9. If the timing circuit 2-8 isoff, the control capacitor 2-6 is allowed to recharge, as describedabove. The timing circuit 2-8 is typically a transistor switch withon/off timing controlled by an integrated circuit timer, which is set topermit discharging of the capacitor 2-6 for a period of the order 15 μsor less. The first step up transformer 2-9 is arranged to raise themedium level input voltage to a high voltage output of around 4500 V.Under control of the timing circuit 2-8, this output is pulsed.

Moving on to step 3, as shown in FIG. 1, the high voltage alternatingcurrent pulses, output from the second step up transformer 2-9 are inputto a second rectifier 2-10, which in this embodiment is a diode. Thepulses are thereby converted into a high-voltage dc signal, in theregion of 4.5 kV. The spark gap 2-13 is connected across the rectifiedoutput from the first transformer 2-9 in parallel with a secondcapacitor 2-11. The rectified signal is then discharged into the sparkgap 2-13 in short impulses, whose duration is controlled by circuitparameters, primarily the inductance of the transformer 2-9 and thevalue of capacitor 2-11. The impulse duration should be no more than 100ns. Giving due consideration to less-flexible factors such astransformer inductance, it is found that the capacitor 2-11 should havecapacitance in the region of 22 pF for satisfactory operation. Theemitter 2-12 is located in the vicinity of the spark gap 2-13 andelectrically isolated therefrom. As a result of the discharging impulsesin the spark gap 2-13, the emitter experiences electro-static energyfluctuations, and the surrounding area is cooled.

FIG. 3 is a diagram showing suitable designs of spark gap 2-13 andemitter 2-12 for use with this invention. FIG. 3 a shows a sideillustration, FIG. 3 b a cross-section along line AA and FIG. 3 c across-section along line BB. The spark gap 2-13 is formed by first 3-1 aand second 3-1 b electrodes separated by a gap, which is typically inthe region of 0.7 mm. The electrodes 3-1 a, b are dome-shaped andtypically made of steel and coated with nickel or chrome. In a preferredembodiment of the invention, the electrodes are sealed in a ceramicchamber containing an argon environment. Other inert gases, in additionto air, are also suitable. The spark gap should however be hermeticallysealed in order to prevent the accumulation of material on theelectrodes, which may impede the discharge of impulses. With this, orsimilar, electrode arrangement, a voltage of over 3000V is required tocause a discharge current to flow through the surrounding gas, resultingin a sparking between the ends of the electrodes 3-1 a,b. The dome shapeis advantageous as it allows sparks to extend across the gap between theelectrodes without being restricted to a base position on the electrode.This extends the life of the electrodes.

The emitter 2-12 abuts the first electrode 3-1 a and is electricallyisolated therefrom. It consists of inner 3-2 and outer 3-4 thin-walledmetal tubes that are coaxially mounted about the electrode lead, at theopposite side of the electrode to the spark gap 2-13. Plastic end caps3-3 located at both ends of the tubes 3-2, 3-4 serve to isolateelectrically the tubes from the electrode and its lead. The tubes 3-2and 3-4 are typically made from electro-plated copper or stainlesssteel. The inner tube 3-2 has an external diameter of around 8 mm andlength of around 9 mm. The outer tube 3-4 has an external diameter ofaround 12 mm and length of about 13 mm. The radial gap between theelectrode 3-1 a and the internal walls of inner tube 3-2 is usually atleast 2 mm to prevent sparks developing within the emitter. The plasticend caps 3-3 extend beyond the circumference of the outer metal tube 3-4to prevent sparks developing between the outer walls of the emitter andthe dome shaped head of the electrode 3-1 a.

During operation of the device, the emitter tubes 3-2 and 3-4 becomecharged electro-statically as a result of the impulse discharges acrossthe spark gap 2-13. As a result of the fluctuating electro-staticcharge, the tubes produce a cooling effect that withdraws natural heatfrom the surrounding environment, typically air.

In order for the emitter to produce its effect, it is important that theimpulse voltage applied across the spark gap 2-13 has certainproperties. In particular it must be a direct current impulse of atleast 3 kV and preferably 4 kV. This voltage should be discharged in atimescale of not longer than 100 ns. With these characteristics animpulse will electro-statically charge an emitter 2-12 located in thevicinity of, but electrically isolated from, the spark gap 2-13.

FIG. 4 is a detailed circuit design for a printed circuit board for thecooling device of this invention. The low voltage direct current powersupply 2-1 may be connected to this circuit at CN2. As statedpreviously, this supply is conveniently provided by a regulated switchedmode mains adaptor or by batteries. Pads P1 and P2 allow an externalswitch to be fitted to control the power to the circuit. The square wavegenerator is indicated by integrated circuit U1. Resistors R1, R2, R3and R4, capacitors C1, C3 and C4, diodes D3 and D4 and transistor Q1control the square wave produced by U1. As will be apparent to oneskilled in the art, if the values of these components are selectedappropriately, transistor Q1 will not overheat. The values indicated inFIG. 4 provide one example of a suitable combination that ensurestransistor Q1 will not normally overheat. The second step up transformer2-3 is represented in this circuit diagram by T1, which is a 1:25 stepup transformer. The square wave generated by U1 is therefore raised(step 1, FIG. 1) to medium voltage by T1. The medium voltage current isrectified by bridge rectifier BR1 (2-4). Current reversals are preventedby diode D1 (2-5). These components, enclosed in the diagram by box 4-1govern the charging, at medium voltage, of control capacitor 2-6 (C7 inFIG. 4).

The medium voltage unidirectional direct current is stored incapacitor(s) C7 and converted into short pulses of energy at a regularfrequency by switch circuit 2-8, transistor Q2 of FIG. 4. Resistors 2-7(R8 and R9) ensure that capacitor 2-6 (C7) is discharged when thecircuit is switched off. Integrated circuits U2 and U3, resistors R5, R6and R7, capacitors C4, C5, C8, C9 and C10, diodes D9 and D10 control theswitching of transistor Q2. This corresponds to step 2, as shown in FIG.1.

The short pulses (of around 15 μs duration) discharged from thecapacitor 2-6 (C7) are raised to high voltage by the first step uptransformer 2-9 (T2), which, in this embodiment, is a 1:20 transformer.The high voltage current is half rectified by diode 2-10 (D2) to createhigh voltage pulses. The high voltage pulses are discharged in impulses,controlled by capacitor 2-11 (C6), of less than 100 ns in spark gap 2-13(FS1). The discharging of capacitor 2-6 (C7) and subsequent raising tohigh voltage impulses is controlled by the components shown in box 4-2in FIG. 4.

Diode D2 should be encapsulated in a polyurethane or silicone sealant toprevent the development of high voltage coronas.

In constructing a cooling device in accordance with this invention, thecircuit shown in FIG. 4 is encased and connected to a source of power.Once the device is operated, impulses are discharged across the sparkgap 2-13 at a rate of around 300 Hz.

It will be clear to one skilled in the art that circuit parameters canbe adjusted to vary the spark discharge characteristics, which in turnaffects the cooling that can be achieved. It is important however inconsidering changes to the circuit to ensure that there is enough energystored in the control capacitor 2-6 to drive the spark emissions at therate and voltages required. That is, the charging part of the circuit4-1 must be capable of providing the energy demanded by the dischargingpart 4-2. For example, increasing the discharge frequency across thespark gap should increase the cooling that can be achieved. As aconsequence however of the control capacitor 2-6 being required to powerthe discharge sparks more frequently the total energy stored (½ CV²)should be increased. Care must be taken in increasing this energy thatthe transformers 2-3, 2-9 are not saturated, with consequent reductionin performance. As a second example, it has been found that a thresholdvoltage of at least 3 kV is required to generate a spark that is capableof providing cooling. Increasing this voltage generally improves coolingperformance, but this effect appears to become saturated at around 4.5-5kV.

1. A cooling device comprising a high voltage source connected to aspark gap (2-13) and controlled by a timing means (2-11), wherein thesource and timing means (2-11) are arranged to generate unidirectionalhigh voltage pulses which are discharged in short and regular impulsesacross the spark gap (2-13) and the device also includes an emitter(2-12) located in the vicinity of an electrode (3-1 a) of the spark gapand electrically isolated therefrom.
 2. A cooling device according toclaim 1 wherein the high voltage source is arranged to provide a voltageof at least 3 kV.
 3. A cooling device according to claim 2 wherein thehigh voltage source is arranged to provide a voltage of at least 4 kV.4. A cooling device according to claim 1 wherein the timing means (2-11)is arranged to limit the discharge to a timescale of less than 100 ns.5. A cooling device according to claim 1 wherein the high voltage sourcecomprises a medium voltage source, timing control means (2-8) for timingpower output from said source in medium voltage pulses, a transformer(2-9) arranged to convert the medium voltage pulses to high voltagepulses and a rectifier (2-10) arranged to convert the high voltagepulses to a unidirectional signal.
 6. A cooling device according toclaim 5 wherein the timing control means comprises a transistor (Q2). 7.A cooling device according to claim 5 wherein the medium voltage sourcecomprises a storage device (2-6) for storing charge at medium voltageand which is discharged by operation of the timing control means (2-8).8. A cooling device according to claim 7 wherein the storage device is acapacitor (2-6).
 9. A cooling device according to claim 7 wherein thestorage device is a bank of capacitors (2-6).
 10. A cooling deviceaccording to claim 8 wherein the capacitor (2-6) is charged by a circuitcomprising a low voltage source (2-1), a pulse generator (2-2) arrangedto produce an alternating signal from the low voltage source, a secondtransformer (2-3) arranged to convert low voltage input to a mediumvoltage output and a rectifier (2-4, 2-5) arranged to rectifyalternating signal input to direct current output.
 11. A cooling deviceaccording to claim 1 wherein the spark gap (2-13) comprises first (3-1a) and second (3-1 b) electrodes sealed within a chamber and separatedby an insulating gap.
 12. A cooling device according to claim 11 whereinthe electrodes (3-1 a, b) are dome shaped.
 13. A cooling deviceaccording to claim 11 wherein the electrodes are made of chrome- ornickel-coated steel.
 14. A cooling device according to claim 11 whereinthe chamber is filled with an inert gas.
 15. A cooling device accordingto claim 14 wherein the inert gas is argon.
 16. A cooling deviceaccording to claim 1 wherein the emitter (2-12) comprises inner (3-2)and outer (3-4) thin-walled coaxial tubes.
 17. A cooling deviceaccording to claim 16 wherein the coaxial tubes (3-2, 3-4) are made frommaterials with good electrical conductivity, such as a ceramic ormetallic material, and coaxially mounted about an electrode connectionlead.
 18. A cooling device according to claim 16 wherein the tubes haveinternal diameters in the range 6 mm to 14 mm.
 19. A cooling deviceaccording to claim 18 wherein the tubes have lengths in the range 7 mmto 20 mm.
 20. A method of generating a cooling effect, the methodcomprising the steps of:— (a) Repeatedly applying a high-voltage,unidirectional pulse of electricity between a pair of electrodes in agaseous environment, thereby causing sparking between the electrodes;and (b) Diffusing a cooling effect resulting from the sparking by meansof an emitter located in the vicinity of the electrodes.
 21. A methodaccording to claim 20 wherein the pulse is of duration less than 100 nsand of voltage higher than 3 kV.